1. Field of the Invention
The present invention relates to an electric punch, and in particular to a battery-operated portable electric punch which punches a plurality of filing holes in a sheet or sheets of paper.
2. Description of the Prior Art
Many types of electric punches are known. One conventional device has middle portions of operation arms supported by respective shafts at the side of respective holders in the manner permitting vertical rotation of the operation arms. A punching block is supported by a shaft at the end of each operation arm so that the punching blocks are vertically movable. A pair of shafts, eccentric with respect to each other, are revolvably inserted into a pair of grooves of identical shape in the rear portions of the respective operation arms.
The two punching blocks are differentially raised and lowered by revolving movement of the two eccentric shafts via their respective operation arms. The grooves in the operation arms are of identical shape, and the eccentric shafts are inserted into different regions of the grooves, causing the revolving movement of one of the operation arms to be smaller and consequently the vertical stroke of the punching block interlocked with this operation arm to be shorter. This presents a problem that the punching action may not be thorough when punching a filing hole in paper. Also, there a sheet or sheets of paper may get caught by the punching blade at the bottom of the punching block while the punching block is being raised after the punching. This can damage the paper.